Transmission and vehicle having transversely mounted transmission and engine arranged in axial direction thereof

ABSTRACT

A vehicle includes an engine, a pair of side frames extending along a vehicle body in a front-rear direction of the vehicle, a transmission adapted to be axially connected with the engine and adapted to be transversely mounted on the vehicle body, includes an input shaft, an output shaft, a first counter shaft, a second counter shaft, a first gear mechanism, a second gear mechanism, a third gear mechanism, and a transmission case, wherein the first and second gear mechanisms are arranged relatively close to the engine, the third gear mechanism is arranged more remote from the engine than the second gear mechanism, the first counter shaft is arranged above the input shaft and the second counter shaft, and the transmission case forms a cut-out portion at an upper portion of a back wall portion of the transmission case.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119to Japanese Patent Application 2007-235824, filed on Sep. 11, 2007, theentire contents of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a vehicle having an engine and atransmission that are connected to each other in an axial directionthereof and that are transversely mounted on the vehicle relative to avehicle body.

BACKGROUND

In order to downsize a transmission and increase output torque, forexample, a transmission apparatus disclosed in JP2002-70960A, adapted toa front-engine front-drive type vehicle to which an engine and atransmission connected in an axial direction thereof are transverselymounted, includes an input shaft, two counter shafts and plural shiftstage gear sets that are arranged in parallel to each other between theinput shaft and each of the counter shafts, thereby shortening length ofthe transmission apparatus in an axial direction thereof withoutreducing number of shift stages. A transmission 1 illustrated in FIG. 5has substantially the same structure as the transmission apparatusdisclosed in the second embodiment of JP2002-70960A. As illustrated inFIG. 5, an input shaft 3 a, first counter shaft 3 b, a second countershaft 3 c and a reverse shaft 3 d are arranged in parallel to each otherwithin a transmission case 2. The first counter shaft 3 b and the secondcounter shaft 3 c are connected to output shafts 8 a and 8 b viareduction gear set 6 a, 6 b and 6 c and a differential mechanism 7. Afirst forward movement gear switching unit 4A forming a 1st shift stageand a 2nd shift stage and a second forward movement gear switching unit4B forming a 3rd shift stage and a 4th shift stage are arranged betweenthe input shaft 3 a and the first counter shaft 3 b so that the secondforward movement gear switching unit 4B is positioned farther away froman engine 10 than the first forward movement switching unit 4A. A thirdforward movement switching unit 4C forming a 5th shift stage and a 6thshift stage is arranged between the input shaft 3 a and the secondcounter shaft 3 c so as to be located at a position substantiallycorresponding to the position where the second forward movement gearswitching unit 4 a is arranged, in an axial direction of the input shaft3 a. Further, a reverse movement gear switching mechanism 4D forming areverse shift stage is arranged between the input shaft 3 a, the secondcounter shaft 3 c and the reverse shaft 3 d so as to be located at aposition substantially corresponding to the position where the firstforward movement gear switching unit 4A is provided, in the axialdirection of the input shaft 3 a. A back wall portion 2 a of thetransmission case 2, substantially corresponding to an area where inputshaft 3 a, the first counter shaft 3 b and the second counter shaft 3 care arranged orthogonally relative to the back wall portion 2 a, isformed to have a flat surface.

FIG. 6 schematically illustrates a forward portion of the vehicle,viewed in a lateral direction thereof, to which a driving unit istransversely mounted at the forward portion of a vehicle body. Thedriving unit is a unit in which the transmission 1 disclosed inJP2002-70960A is connected to the engine 10 in an axial directionthereof. As illustrated in FIG. 6, the driving unit is positionedbetween a pair of side frames 9 extending along both sides of thevehicle body in a front-rear direction thereof. In order to prevent theside frames 9 from interfering with a front axle, forward portions ofthe side frames 9 are curved upwardly. Hence, as illustrated in FIG. 6,the side frame 9 at the left side in FIG. 6 extends along immediate leftof an upper portion of the back wall portion 2 a of the transmissioncase 2 in the front-rear direction of the vehicle.

In order to increase collision safety and vehicle stiffness, across-section of each of the side frames 9 needs to be enlarged and ashape of each of the side frames 9 needs to be linearized. The sideframes 9 a having the enlarged cross-sectional area and the linearizedshape are illustrated with chain double-dashed lines in FIG. 6. As isevident from the position of the side frames 9 a having the enlargedcross-section and illustrated with the chain double-dashed lines in FIG.6, the side frame 9 a at the left side in FIG. 6 interferes with anupper left portion of the back wall portion 2 a of the transmission case2, and the side frame 9 a at the right side in FIG. 6 is positionedcloser to the engine 10. Hence, the driving unit having axiallyconnected engine 10 and transmission 1 may have difficulties when beingtransversely mounted on the vehicle body. A case where the driving unit,in which the engine and the transmission are connected in the axialdirection thereof, is adapted to the front-engine front-drive typevehicle is described above. However, as is the case with thetransmission adapted to the front-engine front-drive type vehicledescribed above, in a case where a similar driving unit is adapted to arear-engine rear-drive type vehicle, the driving unit in which thetransmission 1 and the engine 10 are connected in an axial directionthereof may have difficulties when being transversely mounted on thevehicle body because of the similar reasons explained above.

The transmission apparatus disclosed in JP2002-70960A suggests amodified transmission apparatus in which a portion of the back wall ofthe transmission case positionally corresponding to the second countershaft is arranged closer to the engine, compared to a portion of theback wall positionally corresponding to the first counter shaft, byeliminating one shift stage. However, in the transmission apparatusdisclosed in JP2002-70960A, the portion on the back wall, correspondingto the second counter shaft and positioned closer to the engine thanother portions of the back wall, is positioned at lower portion of thetransmission case, thus resulting in creating a dead space at the backwall portion of the transmission case. Hence, even with the modifiedtransmission apparatus disclosed in JP2002-70960A, the driving unit mayhave difficulties when being transversely mounted on the vehicle.

A need thus exists for a vehicle which is not susceptible to thedrawback mentioned above.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a vehicle includes anengine, a pair of side frames provided at the vehicle so as to extendalong both sides of a vehicle body in a front-rear direction of thevehicle, a transmission adapted to be axially connected with an engineand adapted to be transversely mounted on a vehicle body, including, aninput shaft adapted to be rotatably driven by the engine, an outputshaft connected to a driving wheel, a first counter shaft arranged inparallel to the input shaft and connected to the output shaft, a secondcounter shaft arranged in parallel to the input shaft and connected tothe output shaft, a first gear mechanism between the input shaft and thefirst counter shaft, the first gear mechanism having a first gear set, asecond gear set and a first switching clutch provided between the firstand second gear sets to selectively establish a power transmission pathbetween the input shaft and the first counter shaft via either the firstgear set or the second gear set, a second gear mechanism between theinput shaft and the second counter shaft, the second gear mechanismhaving a third gear set, optionally a fourth gear set and a secondswitching clutch to selectively establish a power transmission pathbetween the input shaft and the second counter shaft via the third gearset, or if present, the fourth gear set, a third gear mechanism betweenthe input shaft and the second counter shaft, the second and third gearmechanisms extending in parallel with one another between the inputshaft and the second counter shaft, the third gear mechanism having afifth gear set, optionally a sixth gear set and a third switching clutchprovided between the fifth and sixth gear sets to establish a powertransmission path established between the input shaft and the secondcounter shaft via the fifth gear set, or if present, the sixth gear set,and a transmission case 12 supporting and covering most of the inputshaft, the first counter shaft, the second counter shaft, the outputshaft, the first gear mechanism, the second gear mechanism and the thirdgear mechanism, wherein the first gear mechanism and the second gearmechanism are arranged relatively close to the engine, the third gearmechanism is arranged at a position more remote from the engine than thesecond gear mechanism, and the first counter shaft is arranged above theinput shaft and the second counter shaft, a driving gear of the secondgear set, serves also as the driving gear of the third gear set and isaxially aligned with the ends of the second and third gear sets closerto the engine, and a driving gear of the first gear set is arranged atan axial distance from the engine substantially corresponding to theaxial location of the third switching clutch, and wherein thetransmission case includes a back wall portion formed with a first backwall portion corresponding to the second gear mechanism and the thirdgear mechanism and a second back wall portion corresponding to the firstgear mechanism and located closer to the engine than the first back wallportion, thereby forming a cut-out portion at an upper portion of theback wall portion, and wherein the transmission is connected to theengine and transversely mounted on the vehicle body so that one of thepair of the side frames extending along the both sides of the vehiclebody in the front-rear direction thereof extends through the cut-outportion.

According to another aspect of the present invention, a transmissionadapted to be axially connected with an engine and adapted to betransversely mounted on a vehicle body, includes an input shaft adaptedto be rotatably driven by the engine, an output shaft connected to adriving wheel, a first counter shaft arranged in parallel to the inputshaft and connected to the output shaft, a second counter shaft arrangedin parallel to the input shaft and connected to the output shaft, afirst gear mechanism between the input shaft and the first countershaft, the first gear mechanism having a first gear set, a second gearset and a first switching clutch provided between the first and secondgear sets to selectively establish a power transmission path between theinput shaft and the first counter shaft via either the first gear set orthe second gear set, a second gear mechanism between the input shaft andthe second counter shaft, the second gear mechanism having a third gearset, optionally a fourth gear set and a second switching clutch toselectively establish a power transmission path between the input shaftand the second counter shaft via the third gear set or, if present, thefourth gear set, a third gear mechanism between the input shaft and thesecond counter shaft, the second and third gear mechanisms extending inparallel with one another between the input shaft and the second countershaft, the third gear mechanism having a fifth gear set, optionally asixth stage gear set and a third switching clutch provided between thefifth and sixth gear sets to selectively establish a power transmissionpath between the input shaft and the second counter shaft via the fifthgear set or, if present, the sixth gear set, and a transmission case 12supporting and covering most of the input shaft, the first countershaft, the second counter shaft, the output shaft, the first gearmechanism, the second gear mechanism and the third gear mechanism,wherein the first gear mechanism and the second gear mechanism arearranged relatively close to the engine, the third gear mechanism isarranged at a position more remote from the engine than the second gearmechanism, and the first counter shaft is arranged above the input shaftand the second counter shaft, a driving gear of the second gear setserves also as the driving gear of the third gear set and is axiallyaligned with the ends of the second and third gear sets closer to theengine, and a driving gear of the first gear set is arranged on theinput shaft at an axial distance from the engine substantiallycorresponding to the axial location of the third switching clutch, andwherein the transmission case includes a back wall portion formed with afirst back wall portion corresponding to the second gear mechanism andthe third gear mechanism and a second back wall portion corresponding tothe first gear mechanism and located closer to the engine than the firstback wall portion, thereby forming a cut-out portion at an upper portionof the back wall portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of the presentinvention will become more apparent from the following detaileddescription considered with the reference to the accompanying drawings,wherein:

FIG. 1 is a view schematically illustrating an entire structure of anexample of a transmission adapted to a vehicle in which axiallyconnected engine and transmission is transversely mounted;

FIG. 2 is a view schematically illustrating the transmission viewed fromthe left side in FIG. 1;

FIG. 3 is a view of a portion of the vehicle, viewed in lateraldirection thereof, at which the axially connected engine andtransmission is transversely mounted;

FIG. 4 is a view illustrating a second embodiment of the transmissionillustrated in FIG. 1;

FIG. 5 is a view schematically illustrating an entire structure of anexample of a conventional transmission; and

FIG. 6 is a sectional view of the vehicle, viewed in lateral directionthereof, at which the axially connected engine and the conventionaltransmission is transversely mounted.

DETAILED DESCRIPTION First Embodiment

A first embodiment of a transmission and a vehicle, to which thetransmission and an engine connected in an axial direction thereof aretransversely mounted, will be described below in accordance with FIGS. 1to 3 of the attached drawings. FIG. 3 schematically illustrates asectional view of a forward portion of the vehicle, viewed in lateraldirection thereof, in a case where the axially connected engine andtransmission of the first embodiment is adapted to a front-enginefront-drive type vehicle. An engine 10 and a transmission 11, connectedwith each other in the axial direction thereof, are transversely mountedbetween forward portions of left and right side frames 13 that serve asprimary strength members and that extend along the both side portions ofa vehicle body in a front-rear direction of the vehicle. Thetransmission 11 is arranged at the left of the engine 10 in FIG. 3. Acut-out portion 12 b, which will be described below, is formed at anupper portion of a back wall portion 12 a of a transmission case 12. Theforward portion of the left side frame 13 of the left and right sideframes 13, whose forward portions are upwardly curved for avoidinginterference with a front axle, extends through the cut-out portion 12 bformed at the upper portion of the back wall portion 12 a of thetransmission case 12.

As illustrated in FIGS. 1 and 2, the transmission 11 includes an inputshaft 15 rotatably driven by the engine 10, an output shaft 19 connectedto driving wheels (not shown), first and second counter shafts 16 and 17and a reverse shaft 18 that are arranged in parallel to the input shaft15 and that are connected to the output shaft 19 via a reduction gearset 28 a, 28 b, 28 c and 28 d, a first forward movement gear switchingunit 20A (a first gear mechanism) arranged between the input shaft 15and the first counter shaft 16, a second forward movement gear switchingunit 20B (a second gear mechanism) and a third forward movement gearswitching unit 20C (a third gear mechanism) each of which is arrangedbetween the input shaft 15 and the second counter shaft 17, a reversemovement gear switching unit 20D (a reverse movement gear mechanism)arranged between the input shaft 15 and the reverse shaft 18, and thetransmission case 12. The transmission case 12 supports the input shaft15, the first and second counter shaft 16 and 17, the reverse shaft 18,the output shaft 19, the first, second, and third forward movement gearswitching units 20A, 20B, 20C and a reduction gear set 28 a, 28 b, 28 cand 28 d, most of which are accommodated therewithin. The reduction gearset 28 a, 28 b, 28 c and 28 d is arranged at a position which is theclosest to the engine 10 among the gear sets within the transmissioncase 12. The first, second and third forward movement gear switchingunits 20A, 20B and 20C are positioned so as to be further away from theengine 10 than the reduction gear set 28 a, 28 b, 28 c and 28 d.

As illustrated in FIGS. 1 and 3, the transmission 11 is arranged at oneside of the engine 10 so as to be connected therewith in the axialdirection of the engine 10. The transmission case 12 is fixed to theengine 10. A left end portion and a middle portion of the input shaft 15in FIG. 1 is rotatably supported at the transmission case 12, and aright end portion of the input shaft 15 is connected to a crank shaft(not shown) of the engine 10 via a clutch (not shown). Both ends of eachof the first counter shaft 16 and the second counter shaft 17 and thereverse shaft 18 are rotatably supported at the transmission case 12.The output shaft 19 is formed with a first shaft 19 a and a second shaft19 b that are coaxially connected via a differential mechanism 29arranged within the transmission case 12. The first and second shafts 19a and 19 b are rotatably supported by the transmission case 12. Further,each outer end portion of each of the first and second shafts 19 a and19 b is connected to the corresponding driving wheel via a joint and adrive shaft (not shown). The smaller reduction gears 28 a, 28 b and 28c, fixed at the first and second counter shafts 16 and 17 and thereverse shaft 18, respectively, engage with the larger reduction gear 28d, having a larger diameter than the reduction gears 28 a, 28 b and 28 cand provided at the differential mechanism 29, thereby connecting thefirst and second counter shafts 16 and 17 and the reverse shaft 18 tothe output shaft 19. ‘Small’, as used in the reduction small gears 28 a,28 b and 28 d, does not refer to specific size thereof, but ratherbecause sizes of the reduction gears 28 a, 28 b, and 28 d are smallerthan the reduction gear 28 d. Similarly, ‘large’, as used in thereduction large gear 28 d, does not refer to a specific size thereof,but rather because a size of the reduction gear 28 d is larger thanother reduction gears 28 a, 28 b and 28 c. Additionally, as illustratedin FIG. 2, the first counter shaft 16 and the reverse shaft 18 arepositioned above the input shaft 15 and the second counter shaft 17.

As illustrated in FIG. 1, the first forward movement gear switching unit20A is arranged at a position relatively close to the engine 10. Thefirst forward movement gear switching unit 20A forms a 1st shift stageand a 2nd shift stage, and includes two pairs of gear sets arrangedbetween the input shaft 15 and the first counter shaft 16, i.e. a 1stshift gear set (first gear set) 21 a, 21 b and a 2nd shift stage gearset (second gear set) 22 a, 22 b, and a first switching clutch 30A. The1st shift stage gear set includes the driving gear 21 a and the drivengear 21 b, and the 2nd shift stage gear set includes the driving gear 22a and the driven gear 22 b. The first switching clutch 30A is arrangedbetween the 1st shift stage gear set 21 a, 22 b and the 2nd shift stagegear set 22 a, 22 b, and establishes a power (torque) transmission pathestablished by each of the 1st shift stage gear set 12 a, 22 b and the2nd shift stage gear set 22 a, 22 b between the input shaft 15 and thefirst counter shaft 16. The driving gear 21 a of the 1st shift stagegear set 21 and 21 b and the driving gear 22 a of the 2nd shift stagegear set 22 a and 22 b are fixed at the input shaft 15, and the drivengear 21 b of the 1st shift stage gear set 21 a and 21 b and the drivengear 22 b of the 2nd shift stage gear set 22 a and 22 b are rotatablyprovided at the first counter shaft 16. The first switching clutch 30Ais provided between the driven gears 21 b and 22 b, and selectivelyconnects either one of the driven gears 21 b and 22 b with rotation ofthe first counter shaft 16.

A known synchromesh mechanism is adapted to the first switching clutch30A. The first switching clutch 30A incorporates therein a clutch hub Lfixed at the first counter shaft 16, a sleeve M spline-engaged with anouter periphery of the clutch hub L so as to be movable in an axialdirection of the first counter shaft 16, and engaging members S1 and S2that are integrally formed at the driven gears 21 b and 22 b,respectively and that are spline-engageable with the sleeve M. When thesleeve M of the first switching clutch 30A is shifted towards the drivengear 21 b by means of a manually or automatically operated shift fork Nfrom a neutral position illustrated in FIG. 1, the sleeve M isspline-engaged with the engaging member S1, and the driven gear 21 b ofthe 1st shift stage gear set 21 a and 21 b is connected to the rotationof the first counter shaft 16. As a result, the 1 st shift stage isestablished. Further, when the sleeve M is shifted towards the drivengear 22 b by means of the shift fork N from the position where the 1stshift stage is established, firstly the engaging member S1 is disengagedfrom the sleeve M, and the sleeve M is returned to the neutral position.When the sleeve M is shifted further towards the driven gear 22 b, thesleeve M is spline-engaged with the engaging member S2, and the drivengear 22 b of the 2nd shift stage gear set 22 a and 22 b is connected tothe rotation of the first counter shaft 16. As a result, the 2nd shiftstage is established. When the sleeve M is shifted towards the drivengear 21 b from the position where the 2nd shift stage is established,the sleeve M is returned to the neutral position.

As is the case with the first forward movement gear switching unit 20A,the second forward movement gear switching unit 20B is arranged at aposition relatively close to the engine 10. The third forward movementgear switching unit 20C is arranged at the position more remote from theengine 10 than the second forward movement gear switching unit 20B. Thesecond forward movement gear switching unit 20B forms a 3rd shift stageand a 4th shift stage, and includes a 3rd shift stage gear set (thirdgear set) 23 a, 23 b and a 4th shift stage gear set (fourth gear set) 24a, 24 b, both of which are arranged between the input shaft 15 and thesecond counter shaft 17, and a second switching clutch 30B arrangedbetween the 3rd and second 4th stage gear sets. The 3rd shift stage gearset includes the driving gear 23 a and the driven gear 23 b, and the 4thshift stage gear set includes the driving gear 24 a and the driven gear24 b. The second forward movement gear switching unit 20B is structuredsubstantially the same as the first forward movement gear switching unit20A. When a sleeve M of the second switching clutch 30B is shiftedtowards the driven gear 23 b of the 3rd shift stage gear set 23 a and 23b from a neutral position illustrated in FIG. 1, the 3rd shift stage isestablished by the substantially same manner as, for example, the 2ndshift stage is established. When the sleeve M is shifted towards thedriven gear 24 b of the 4th shift stage gear set 24 a and 24 b from theposition where the 3rd shift stage is established, the sleeve M isreturned to the neutral position. When the sleeve M is further shiftedtowards the driven gear 24 b from the neutral position, the 4th shiftstage is established. Further, when the sleeve M is shifted towards thedriven gear 23 b from the position where the 4th shift stage isestablished, the sleeve M is returned to the neutral position.

The third forward movement gear switching unit 20C forms a 5th shiftstage and a 6th shift stage, and includes a 5th shift stage gear set(fifth gear set) 25 a, 25 b and a 6th shift stage gear set (sixth gearset) 26 a, 26 b, both of which are arranged between the input shaft 15and the second counter shaft 17, and a third switching clutch 30Carranged between the 5th and 6th shift stage gear sets. The 5th shiftstage gear set includes the driving gear 25 a and the driven gear 25 b,and the 6th shift stage gear set includes the driving gear 26 a and thedriven gear 26 b. The third forward movement gear switching unit 20C isstructured substantially the same as the first and second forwardmovement gear switching units 20A and 20B. When a sleeve M of the thirdswitching clutch 30C is shifted towards the driven gear 25 b of the 5thshift stage gear set 25 a and 25 b from a neutral position illustratedin FIG. 1, the 5th shift stage is established by the substantially samemanner as, for example, the 1st shift stage is established. When thesleeve M is shifted towards the driven gear 26 b of the 6th shift stagegear set 26 a and 26 b from the position where the 5th shift stage isestablished, the sleeve M is returned to the neutral position. When thesleeve M is further shifted towards the driven gear 26 b from theneutral position, the 6th shift stage is established. Further, when thesleeve M is shifted towards the driven gear 25 b from the position wherethe 6th shift stage is established, the sleeve M is returned to theneutral position.

The driving gear 22 a of the 2nd shift stage gear set 22 a and 22 b,arranged at the position relatively close to the engine 10 at the firstforward movement gear switching unit 20A, is fixed at the input shaft 15and serves also as the driving gear 23 a of the 3rd shift stage gear set23 a and 23 b arranged at the position relatively close to the engine 10at the second forward movement gear switching unit 20B. The driving gear21 a of the 1st shift stage gear set 21 a and 21 b, arranged at theposition more remote from the engine 10 at the first forward movementgear switching unit 20A than the 2nd shift stage gear set 22 a and 22 b,is fixed at the input shaft 15 at the position substantiallycorresponding to the third switching clutch 30C of the third forwardmovement gear switching unit 20C in the axial direction thereof. That isto say, the driving gear 21 a of the 1st shift stage gear set 21 a and21 b is fixed at the input shaft 15 so as to be arranged between thedriving gear 25 a of the 5th shift stage gear set 25 a, 25 b and thedriving gear 26 a of the 6th shift stage gear set 26 a, 26 b of thethird forward movement gear switching unit 20C.

As illustrated in FIGS. 1 and 2, the reverse movement gear switchingunit 20D includes a reverse gear set 27, arranged between the inputshaft 15, the first counter shaft 16 and the reverse shaft 18, and areverse movement switching clutch 30D that is configured to establish apower transmission path established by the reverse gear set 27 betweenthe input shaft 15 and the reverse shaft 18. The reverse gear set 27 isformed with a driving gear 27 a, an idler gear 27 b and a driven gear 27c. The driving gear 27 a and the idler gear 27 b serve also as the 1stshift stage gear set 21 a and 21 b, respectively, arranged further awayfrom the engine 10 at the first forward movement gear switching unit 20Athan the 2nd shift stage gear set 22 a and 22 b. Further, the drivengear 27 c is rotatably supported at the reverse shaft 18 and is engagedwith the idler gear 27 b (driven gear 21 b) so that the driven gear 27 cis connectable with rotation of the reverse shaft 18 by means of thereverse movement switching clutch 30D arranged at a position relativelyclose to the engine 10 at the reverse movement gear switching unit 20D.The reverse movement switching clutch 30D has substantially the samestructure as the first switching clutch 30A except that the reversemovement switching clutch 30D includes only an engaging member SR fixedat the driven gear 27 c, arranged at one side of the reverse movementswitching clutch 30D, in an axial direction of the reverse shaft 18.When a sleeve M of the reverse movement switching clutch 30D is shiftedtowards the driven gear 27 c from a neutral position illustrated in FIG.1 by means of a shift fork N, the sleeve M is spline-engaged with theengaging member SR, and the driven gear 27 c of the reverse gear set 27is connected to the rotation of the reverse shaft 18. As a result, areverse shift stage is established. When the sleeve M is shifted towardsthe reduction gear 28 c from the position where the reverse shift stageis established, the sleeve M is disengaged from the engaging member SR,and the reverse shift stage is cancelled.

In the above-described first embodiment, the first forward movement gearswitching unit 20A and the second forward movement gear switching unit20B are arranged at the positions relatively close to the engine 10within the transmission case 12, and the third forward movement gearswitching unit 20C is arranged more remote from the engine 10 than thesecond forward movement gear switching unit 20B. The 1st shift stagegear set 21 a and 21 b, arranged more remote from the engine 10 at thefirst forward movement gear switching unit 20A than the 2nd shift stagegear set 22 a and 22 b, are arranged between the 5th shift stage gearset 25 a, 25 b and the 6th shift stage gear set 26 a, 26 b of the thirdforward movement gear switching unit 20C, in the axial direction of theinput shaft 15. Further, the 1st shift stage gear set 21 a and 21 bsevere also as the driving gear 27 a and the idler gear 27 b,respectively, of the reverse movement gear switching unit 20D arrangedfurther away from the engine 10 than the reverse movement switchingclutch 30D. Therefore, a farthest end portion of each of the firstforward movement gear switching unit 20A and the reverse movement gearswitching unit 20D from the engine 10 is arranged closer to the engine10 than a farthest end portion of the third forward movement gearswitching unit 20C from the engine 10 in the axial direction of theinput shaft 15. Further, the first counter shaft 16, at which the drivengear 21 b of the first forward movement gear switching unit 20A servingalso as the idler gear 27 b of the reverse gear set 27 is provided, andthe reverse shaft 18, at which the driven gear 27 c is provided, arearranged above the input shaft 15 and the second counter shaft 17 atwhich the third forward movement gear switching unit 20C is provided, asillustrated in FIG. 2. Therefore, as illustrated in FIGS. 1 and 3, thetransmission case 12, located at the opposite side of the engine 10, isformed to have the first back wall portion 12 a1 corresponding to thesecond and third forward movement gear switching units 20A and 20B andthe second back wall portion 12 a2 corresponding to a portion of thefirst forward movement gear switching unit 20A and the reverse movementgear switching unit 20D arranged at the first counter shaft 16 and thereverse shaft 18, wherein the second back wall portion 12 a2 is locatedcloser to the engine 10 than the first back wall portion 12 a1 formedbelow the second back wall portion 12 a2 . As a result, the transmissioncase 12 forms the cut-out portion 12 b at the upper portion of the backwall portion 12 a.

In the above-described embodiment, the transmission case 12 forms thecut-out portion 12 b at the back wall portion 12 a thereof. Hence, asillustrated in FIG. 3, in a case where the transmission 11 and theengine 10 are arranged in the axial direction thereof so as to beintegrally connected with each other and then the integrally and axiallyconnected transmission 11 and engine 10 is transversely mounted at theforward portion of the vehicle body, the upwardly curved forward portionof one of the right and left side frames 13, serving as the strengthmember, is arranged so as to extend through the cut-out portion 12 b ofthe transmission case 12. As a result, even in a case where axiallyconnected transmission 11 and the engine 10 of the first embodiment isadapted to a vehicle having side frames having the enlargedcross-sectional shapes and linearized shapes, as illustrated in FIG. 3,one of the side frames 13 is prevented from interfering with thetransmission case 12 because the one of the side frames 13 extendsthrough the cut-out portion 12 b of the transmission case 12, comparedto a case where the conventional transmission 1 interferes with one ofthe side frames 9 a having the enlarged cross-sectional shapes andlinearized shapes when the conventional transmission 1 and the engine 10are axially connected and transversely mounted on the vehicle body, asillustrated in FIG. 6. Hence, the axially connected transmission 11 andengine 10 is transversely mountable on the vehicle body without causinginterference between one of the side frames 13 and the transmission case12.

In the above-described first embodiment, the driving gear 22 a of the2nd shift stage gear set 22 a and 22 b, arranged at the positionrelatively close to the engine 10 at the first forward movement gearswitching unit 20A, is fixed at the input shaft 15 and serves also asthe driving gear 23 a of the 3rd shift stage gear set 23 a and 23 b,arranged at the position relatively close to the engine 10 at the secondforward movement gear switching unit 20B. As a result, one of pluralgears provided at the input shaft 15 is eliminated, compared to theconventional transmission apparatus. Therefore, the structure of thetransmission 11 is simplified, and length of the input shaft 15 and thecounter shaft 17 are shortened, which results in shortening length ofthe transmission case 12 in the axial direction of the input shaft 15.

Second Embodiment

A second embodiment of an example of a modified transmission 11′ will bedescribed below in accordance with FIG. 4. The modified transmission 11′has substantially the same structure as the transmission 11 described inthe above-mentioned first embodiment except that a reverse movement gearswitching unit 20D′ of the modified transmission 11′ has a differentstructure from the reverse movement gear switching unit 20D of theabove-described transmission 11 of the first embodiment. Therefore,differences between the modified transmission 11′ and theabove-described transmission 11 will be mainly described below. In themodified transmission 11′, a second idler year 27 b2 , whose diameter issmaller than a first idler gear 27 b1 of a reverse gear set 27A, isintegrally and axially formed at the first idler gear 27 b1 so as to bepositioned between the first idler gear 27 b1 and the engaging member S1of the first switching clutch 30A, so that a driving gear 27 c′ isengaged with the second idler gear 27 b2 . Further, a reverse movementswitching clutch 30D′ of the modified transmission 11′ is arranged atthe position more remote from the engine 10 than the driven gear 27 c′,and further, the reverse movement switching clutch 30D′ is arranged atthe reverse shaft 18 so as not to be positioned farther away from theengine 10 than the 1st shift stage gear set 21 a and 21 b in the axialdirection of the input shaft 15. The modified transmission 11 ′ isstructured the same as the transmission 11 of the first embodimentexcept for the reverse movement gear switching unit 20D. Hence, detailedexplanations on structures of other parts of the modified transmission11′ will be omitted.

As is the case with the above-described transmission 11 of the firstembodiment, as illustrated in FIG. 4, the transmission case 12, locatedat the opposite side of the engine 10, is formed to have the first backwall portion 12 a1 corresponding to the second and third forwardmovement gear switching units 20A and 20B and the second back wallportion 12 a2 corresponding to a portion of the first forward movementgear switching unit 20A and the reverse movement gear switching unit 20Darranged at the first counter shaft 16 and the reverse shaft 18, whereinthe second back wall portion 12 a2 is located closer to the engine 10than the first back wall portion 12 a1 arranged below the second backwall portion 12 a2 . As a result, the transmission case 12 forms thecut-out portion 12 b at the upper portion of the back wall portion 12 a.As a result, even in a case where axially connected transmission 11 ′and the engine 10 of the first embodiment is adapted to a vehicle havingside frames having the enlarged cross-sectional shapes and linearizedshapes, as illustrated in FIG. 3, one of the side frames 13 is preventedfrom interfering with the transmission case 12 because the one of theside frames 13 extends through the cut-out portion 12 b of thetransmission case 12, compared to a case where the conventionaltransmission 1 interferes with one of the side frames 9 a having theenlarged cross-sectional shapes and linearized shapes when theconventional transmission 1 and the engine 10 are axially connected andtransversely mounted on the vehicle body. Hence, the axially connectedtransmission 11′ and engine 10 is transversely mountable on the vehiclebody without causing interference between one of the side frames 13 andthe transmission case 12.

In the second embodiment of the modified transmission 11′, because thesecond idler gear 27 b2 , which is integrally formed with the firstidler gear 27 b1 in the axial direction of the first counter shaft 16and is engaged with the driven gear 27 c′, is formed to have a smallerdiameter than the first idler gear 27 b1 (i.e. a reduction gear ratio ofthe reverse gear set 27A between the input shaft 15 and the reverseshaft 18 is determined on the basis of a gear ratio between the drivinggear 27 a′ and the first idler gear 27 b1 and a gear ratio between thesecond idler gear 27 b2 and the driven gear 27 c′), a diameter of thedriven gear 27 c′ may be reduced in a case where the reduction gearratio between the input shaft 15 and the reverse shaft 18 of the secondembodiment is set as the same level of the reduction gear ratio betweenthe input shaft 15 and the reverse shaft 18 of the first embodiment inwhich the idler gear 27 b is engaged with the driving gear 27 a and thedriven gear 27 c (i.e. the reduction gear ratio of the reverse gear set27 between the input shaft 15 and the reverse shaft 18 is determined onthe basis of a gear ratio between the driving gear 27 a and the drivengear 27 c). As a result, a protruding amount of the transmission case 12because of the reverse movement gear switching unit 20D′ may be reduced,which allows the axially and integrally connected modified transmission11′ and engine 10 to be easily transversely mounted on the vehicle body.Alternatively, by integrally and axially combining two gears whosediameters differ from each other as a idler gear, the reduction gearratio between the input shaft 15 and the reverse shaft 18 is changeableto any desired reduction gear ratio without talking mountability of theaxially connected modified transmission 11′ and engine 10 to the vehiclebody into consideration.

In the second embodiment of the modified transmission 11′, the reversemovement switching clutch 30D′ is provided at the position more remotefrom the engine 10 than the driven gear 27 c′, however, the reversemovement switching clutch 30D′ may be arranged at a position closer tothe engine 10 relative to the driven gear 27 c′. In a case where thereverse movement switching clutch 30D′ is arranged at the positioncloser to the engine 10 relative to the driven gear 27 c′, a rear endportion of the reverse movement gear switching unit 20D′ is positionedfurther closer to the engine 10 than the rear end portion of the firstforward movement gear switching unit 20A, compared to the case where thereverse movement switching clutch 30D′ is arranged further away from theengine 10 than the driven gear 27 c′. In the case where the reversemovement switching clutch 30D′ is arranged at the position closer to theengine 10 relative to the driven gear 27 c′, a portion of the secondback wall portion 12 a2 corresponding to the reverse movement switchingclutch 30D′ of the second back wall portion 12 a2 of the back wallportion 12 a located more remote from the engine 10 is positioned closerto the engine 10, which results in enlarging the cut-out portion 12 bformed at the upper portion of the back wall portion 12 a.

The first and second embodiments describe the transmission having thereverse movement gear switching unit 20D (20D′). However, the presentinvention described in the first and second embodiments is adaptable toa transmission not having a reverse movement gear switching unit. Evenin a case where the present invention is adapted to the transmission nothaving the reverse movement gear switching unit, most of the effects andadvantages described above in the first and second embodiments will beachieved.

Further, in the transmission 1 (11′) of the first and secondembodiments, the first forward movement gear switching unit 20A includesthe 1st shift stage gear set 21 a, 21 b, the 2nd shift stage gear set 22a, 22 b and the first switching clutch 30A that is provided therebetweenand established the power transmission path established by each of the1st shift stage gear set 21 a, 21 b and the 2nd shift stage gear set 22a, 22 b between the input shaft 15 and the first counter shaft 16, thesecond forward movement gear switching unit 20B includes the 3rd shiftstage gear set 23 a, 23 b, the 4th shift stage gear set 24 a, 24 b andthe second switching clutch 30B that is provided therebetween andestablishes the power transmission path established by each of the 3rdshift stage gear set 23 a, 23 b and the 4th shift stage gear set 24 a,24 b between the input shaft 15 and the second counter shaft 17, and thethird forward movement gear switching unit 20C includes the 5th shiftstage gear set 25 a, 25 b, the 6th shift stage gear set 26 a, 26 b andthe third switching clutch 30C that is provided therebetween andestablishes the power transmission path established by each of the 5thshift stage gear set 25 a, 25 b and the 6th shift stage gear set 26 a,26 b between the input shaft 15 and the second counter shaft 17.Accordingly, the transmission 11 (11′) is structured to have six shiftstages which is a maximum number of shift stages for a transmissionhaving three forward movement gear switching units. Hence, output torqueof the transmission 11 (11′) is increased. The present invention is notlimited to the above-described first and second embodiments, but one ormore of the first, second and third forward movement gear switchingunits 20A, 20B and 20C may include only one forward movement shift stagegear set.

In the above-described first and second embodiments, the third forwardmovement gear switching unit 20C is formed with the 5th shift stage gearset (fifth forward movement shift stage gear set) 25 a, 25 b, the 6thshift stage gear set (sixth forward movement shift stage gear set) 26 a,26 b, and the third switching clutch 30C provided therebetween. The 1stshift stage gear set (first forward movement shift stage gear set) 21 aand 21 b, arranged at the input shaft 15 so as to substantiallycorrespond to the third switching clutch 30C in the axial direction ofthe input shaft 15, is positioned between the 5th shift stage gear set25 a, 25 b and the 6th shift stage gear set 26 a, 26 b. The presentinvention is not limited to the above-described structure, but the thirdforward movement gear switching unit of the transmission may includeonly one forward movement shift stage gear set, for example, the 6thshift stage gear set 26 a and 26 b may be removed from the third forwardmovement gear switching unit 20C of the above-described embodiments. Inthe case where the third forward movement gear switching unit includesonly one forward movement shift stage gear set, the 1 shift stage gearset (first forward movement shift stage gear set) 21 a and 21 b ispositioned closer to the engine 10 than the 5th shift stage gear set 25a and 25 b. As is the case with the above-described embodiments, even inthe case where the third forward movement gear switching unit 20Cincludes only one forward movement shift stage gear set, the stepwiselydepressed cut-out portion 12 b is formed at the upper back wall portion12 a of the transmission case 12, and the effects and advantagesdescribed above are achievable.

In the above-described first and second embodiments, the first forwardmovement shift stage gear set is assigned as the 1st shift stage gearset 21 a and 21 b, the second forward movement shift stage gear set isassigned as the 2nd shift stage gear set 22 a and 22 b, the thirdforward movement shift stage gear set is assigned as the 3rd shift stagegear set 23 a and 23 b, the fourth forward movement shift stage gear setis assigned as the 4th shift stage gear set 24 a and 24 b, the fifthforward movement shift stage gear set is assigned as the 5th shift stagegear set 25 a and 25 b, and the sixth forward movement shift stage gearset is assigned as the 6th shift stage gear set 26 a and 26 b. However,each shift stage may be assigned at any desired forward movement shiftstage gear set arranged at the positions illustrated in FIGS. 1 and 4.

Further, in the above-described first and second embodiments, the casewhere the axially connected transmission 11 (11′) and engine 10 isadapted to the front-engine front-drive type vehicle is described above.The present invention is not limited to be adapted to the front-enginefront-drive type vehicle, but the present invention is also adaptable toa rear-engine rear-drive type vehicle.

Accordingly, the first forward movement gear switching unit 20A and thesecond forward movement gear switching unit 20B are arranged relativelyclose to the engine 10 within the transmission case 12, and the thirdforward movement gear switching unit 20C is arranged more remote fromthe engine 10 than the second forward movement gear switching unit 20B.The first counter shaft 16 is arranged above the input shaft 15 and thesecond counter shaft 17. The driving gear 22 a of the 2nd shift stagegear set 22 a and 22 b arranged relatively close to the engine 10 at thefirst forward movement gear switching unit 20A is fixed at the inputshaft 15 and serves also as the driving gear 23 a of the 3rd shift stagegear set 23 a and 23 b arranged relatively close to the engine 10 at thesecond forward movement gear switching unit 20B. Further, the drivinggear 21 a of the 1st shift stage gear set 21 a and 21 b, arranged moreremote from the engine 10 at the first forward movement gear switchingunit 20A than the 2nd shift stage gear set 22 a and 22 b, is provided atthe input shaft 15 at the position substantially corresponding to theposition where the third switching clutch 30C of the third forwardmovement gear switching unit 20C is provided, in the axial direction ofthe input shaft 15. As a result, the transmission case 12, located atthe opposite side of the engine 10, is formed to have the first backwall portion 12 a1 corresponding to the second and third forwardmovement gear switching units 20A and 20B and the second back wallportion 12 a2 corresponding to the portion of the first forward movementgear switching unit 20A, wherein the second back wall portion 12 a2 islocated closer to the engine 10 than the first back wall portion 12 a1arranged below the second back wall portion 12 a2 . As a result, thetransmission case 12 forms the cut-out portion 12 b at the upper portionof the back wall 12 a. By adapting the above-structured transmission 11(11′), the transmission 11 (11′) and the engine 10 are connected in theaxial direction thereof, and the axially connected transmission 11 (11′)and engine 10 is transversely mounted on the vehicle body so that one ofthe side frames 13, extending along the both sides of the vehicle bodyin the front-rear direction thereof, extends through the cut-out portion12 b of the transmission case 12. As a result, even in a case whereaxially connected transmission 11 (11′) and the engine 10 of the firstembodiment is adapted to a vehicle having side frames having theenlarged cross-sectional shapes and linearized shapes, as illustrated inFIG. 3, one of the side frames 13 is prevented from interfering with thetransmission case 12 because the one of the side frames 13 extendsthrough the cut-out portion 12 b of the transmission case 12, comparedto a case where the conventional transmission 1 interferes with one ofthe side frames 9 a having the enlarged cross-sectional shapes andlinearized shapes when the conventional transmission 1 and the engine 10are axially connected and transversely mounted on the vehicle body, asillustrated in FIG. 6. Hence, the axially connected transmission 11 (11′) and engine 10 is transversely mountable on the vehicle body withoutcausing the interference between one of the side frames 13 and thetransmission case 12. Further, as the driving gear 22 a of the 2nd shiftstage gear set 22 a and 22 b of the first forward movement gearswitching unit 20A serves also as the driving gear 23 a of the 3rd shiftstage gear set 23 a and 23 b of the second forward movement gearswitching unit 20B, one of the driving gears is eliminated. As a result,the structure of the transmission 11 (11′) is simplified and thetransmission 11 (11′) is downsized. Moreover, as the driving gear 21 aof the 1st shift stage gear set 21 a and 21 b of the first forwardmovement gear switching unit 20A is provided at the input shaft 15 atthe position substantially corresponding to the position where the thirdswitching clutch 30C of the third forward movement gear switching unit20C is provided, in the axial direction of the input shaft 15, thelengths of the second and third forward movement gear switching units20B and 20C, which are arranged in parallel to each other in the axialdirection of the input shaft 15, are not elongated. Hence, theprotruding amount of the first back wall portion 12 a1 of the back wall12 a of the transmission 11 (11′) from the engine 10 is not increased.

According to the embodiments, the transmission 11 (11′) transverselymounted on the vehicle includes the reverse movement gear switching unit20D (20D′) including the reverse shaft 18 arranged in parallel to theinput shaft 15 and connected to the output shaft 19, the reverse gearset 27 (27A) provided between the input shaft 15 and the reverse shaft18 and the reverse movement switching clutch 30D (30D′) establishing thepower transmission path established by the reverse gear set 27 (27A)between the input shaft 15 and the reverse shaft 18, wherein the 1stshift stage gear set 21 a and 22 b arranged more remote from the engine10 than the 2nd shift stage gear set 22 a and 22 b is set as the gearset for the low speed shift stage, the reverse gear set 27 (27A)includes the driving gear 27 a (27 a′) provided at the input shaft 15,the driven gear 27 c (27 c′) rotatably supported at the reverse shaft 18and connected to the rotation of the reverse shaft 18 by means of thereverse movement switching clutch 30D (30D′) and the idler gear 27 b (27b1 /27 b2 ) rotatably supported at the first counter shaft 16 andengaged with the driving gear 27 a (27 a′) and the driven gear 27 c (27c′), wherein the driving gear 27 a (27 a′) and the idler gear 27 b (27b1 ) of the reverse gear set 27 (27A) serve also as the driving gear 21a and the driven gear 21 b of the 1st shift stage gear set provided atthe first forward movement gear switching unit 20A, respectively,arranged more remote from the engine 10 than the 2nd shift stage gearset.

Accordingly, the transmission 11 (11′) further includes the reverseshaft 18 arranged in parallel to the input shaft 15 and connected to theoutput shaft 19, and the reverse movement gear switching unit 20D (20D′)provided between the input shaft 15 and the reverse shaft 18 and formedwith the pair of the reverse gear set 27 (27A) and the reverse movementswitching clutch 30D that is configured to establish the powertransmission path established by the reverse gear set 27 between theinput shaft 15 and the reverse shaft 18. The forward movement shiftstage gear set 21 a and 21 b of the first forward movement gearswitching unit 20A arranged further away from the engine 10 is a gearset for low speed shift stage. The reverse gear set 27 (27A) is formedwith the driving gear 27 a (27 a′) provided at the input shaft 15, thedriven gear 27 c (27 c′) rotatably supported at the reverse shaft 18 andconnected to the rotation of the reverse shaft 18 by the reversemovement switching clutch 30D, and the idler gear 27 b (27 b1 , 27 b2 )rotatably supported at the first counter shaft 16 and engaged with thedriving gear 27 a (27 a′) and the driven gear 27 c (27 c′). The drivinggear 27 a (27 a′) and the idler gear 27 b (27 b1 ) of the reverse gearset 27 (27A) serve also as the 1st shift stage gear set 21 a and 21 b,respectively, arranged more remote from the engine 10 than the 2nd shiftstage gear set 22 a and 22 b of the first forward movement gearswitching unit 20A. Accordingly, the reverse movement gear switchingunit 20D (20D′) provided at the input shaft 15, the first counter shaft16 and the reverse shaft 18 is not arranged farther from the engine 10than the 1st shift stage gear set 21 a and 21 b arranged more remotefrom the engine 10 at first forward movement gear switching unit 20Athan the 2nd shift stage gear set 22 a and 22 b. Hence, a size of thecut-out portion 12 b formed at the upper portion of the back wallportion 12 a is not reduced. Therefore, even in the case where thereverse movement gear switching unit 20D (20D′) is provided within thetransmission case 12, one of the side frames 13 is provided so as toextend through the cut-out portion 12 b in the front-rear direction ofthe vehicle, so that one of the side frames 13 does not interfere withthe transmission case 12. As a result, the axially connected engine 10and transmission 11 (11′) is transversely mountable on the vehicle body.Further, as the driving gear 27 a (27 a′) and the idler gear 27 b (27 b1) serve also as the 1st shift stage gear set 21 a and 21 b arranged moreremote from the engine 10 at the first forward movement gear switchingunit 20A than the 2nd shift stage gear set 22 a and 22 b, one of theplural gears provided within the transmission case 12 is eliminated,which resulting in simplifying the structure of the transmission 11(11′) and downsizing the transmission 11 (11′). As the 1st shift stagegear set 21 a and 21 b of the first forward movement gear switching unit20A, serving also as the driving gear 27 a of the reverse gear set 27,is the gear of the low speed shift stage. Hence, the reduction gearratio of the reverse gear set 27 is easily increased.

According to the embodiments, the idler gear further includes the firstidler gear 27 b1 rotatably supported at the first counter shaft 16 andengaged with the driving gear 27 a′, and the second idler gear 27 b2 ,whose diameter is smaller than that of the first idler gear 27 b1 ,integrally formed at the first idler gear 27 a′ in an axial direction ofthe first counter shaft 16 and engaged with the driven gear 27 c′,wherein the driving gear 27 a′ and the first idler gear 27 b1 of thereverse gear set 27A serve also as the driving gear 21 a and the drivengear 21 b of the 1st shift stage gear set provided at the first forwardmovement gear switching unit 20A, respectively.

Accordingly, the second idler gear 27 b2 , whose diameter is smallerthan the diameter of the first idler gear 27 b1 , is integrally formedat the first idler gear 27 b1 of the reverse gear set 27A in the axialdirection of the first counter shaft 16. The first idler gear 27 b1 isengaged with the driving gear 27 a′ and the second idler gear 27 b2 isengaged with the driving gear 27 c′. The diameter of the driven gear 27c′ may be reduced in a case where the reverse gear set 27A is reduced intwo stages, i.e. in a case where the reduction gear ratio of the reversegear set 27A is determined on the basis of the gear ratio between thedriving gear 27 a and the first idler gear 27 b1 and the gear ratiobetween the second idler gear 27 b2 and the driven gear 27 c′. Hence,even in a case where the reverse movement gear switching unit 20D′ isprovided within the transmission case 12, the protruding amount of thetransmission case 12 from the engine 10 is reduced, so that thetransmission 11′ is easily mountable to the vehicle body.

According to the embodiments, the first forward movement gear switchingunit 20A includes the 1st shift stage gear set 21 a and 21 b, the 2ndshift stage gear set 22 a and 22 b and the first switching clutch 30Aarranged therebetween and establishing the power transmission pathestablished by each of the 1st shift stage gear set and the 2nd shiftstage gear set between the input shaft 15 and the first counter shaft16, the second forward movement gear switching unit 20B includes the 3rdshift stage gear set 23 a and 23 b, the 4th shift stage gear set 24 aand 24 b and the second switching clutch 30B arranged therebetween andestablishing the power transmission path established by each of the 3rdshift stage gear set and the 4th shift stage gear set between the inputshaft 15 and the second counter shaft 17, and the third forward movementgear switching unit 20C includes the 5th shift stage gear set 25 a and25 b, the 6th shift stage gear set 26 a and 26 b and the third switchingclutch 30C arranged therebetween and establishing the power transmissionpath established by each of the 5th shift stage gear set and the 6thshift stage gear set between the input shaft 15 and the second countershaft 17.

Accordingly, the first forward movement gear switching unit 20A includesthe 1st shift stage gear set 21 a, 21 b, the 2nd shift stage gear set 22a, 22 b, and the first switching clutch 30A that is provided between the1st shift stage gear set 21 a, 21 b and the 2nd shift stage gear set 22a, 22 b and establishes the power transmission path established by eachof the 1st shift stage gear set 21 a, 21 b and 2nd shift stage gear set22 a, 22 b between the input shaft 15 and the first counter shaft 16.The second forward movement gear switching unit 20B includes the 3rdshift stage gear set 23 a, 23 b, 4th shift stage gear set 24 a, 24 b,and the second switching clutch 30B that is provided between the 3rdshift stage gear set 23 a, 23 b and the 4th shift stage gear set 24 a,24 b and establishes the power transmission path established by each ofthe 3rd shift stage gear set 23 a, 23 b and the 4th shift stage gear set24 a, 24 b between the input shaft 15 and the second counter shaft 17.The third forward movement gear switching unit 20C includes the 5thshift stage gear set 25 a, 25 b, the 6th shift stage gear set 26 a, 26b, and the third switching clutch 30C that is provided between the 5thshift stage gear set 25 a, 25 b and the 6th shift stage gear set 26 a,26 b and establishes the power transmission path established by each ofthe 5th shift stage gear set 25 a, 25 b and the 6th shift stage gear set26 a, 26 b between the input shaft 15 and the second counter shaft 17.Accordingly, the transmission 11 (11′) has the six shift stages, whichis the maximum number of shift stages for a transmission having threeforward movement gear switching units. Hence, the output torque of thetransmission 11 (11′) is increased.

The principles, preferred embodiment and mode of operation of thepresent invention have been described in the foregoing specification.However, the invention which is intended to be protected is not to beconstrued as limited to the particular embodiments disclosed. Further,the embodiments described herein are to be regarded as illustrativerather than restrictive. Variations and changes may be made by others,and equivalents employed, without departing from the spirit of thepresent invention. Accordingly, it is expressly intended that all suchvariations, changes and equivalents which fall within the spirit andscope of the present invention as defined in the claims, be embracedthereby.

1. A vehicle comprising: an engine; a pair of side frames provided atthe vehicle so as to extend along both sides of a vehicle body in afront-rear direction of the vehicle; a transmission adapted to beaxially connected with the engine and adapted to be transversely mountedon the vehicle body, including: an input shaft adapted to be rotatablydriven by the engine; an output shaft connected to a driving wheel; afirst counter shaft arranged in parallel to the input shaft andconnected to the output shaft; a second counter shaft arranged inparallel to the input shaft and connected to the output shaft; a firstgear mechanism between the input shaft and the first counter shaft, thefirst gear mechanism having a first gear set, a second gear set and afirst switching clutch provided between the first and second gear setsto selectively establish a power transmission path between the inputshaft and the first counter shaft via either the first gear set or thesecond gear set; a second gear mechanism between the input shaft and thesecond counter shaft, the second gear mechanism having a third gear set,optionally a fourth gear set and a second switching clutch toselectively establish a power transmission path between the input shaftand the second counter shaft via the third gear set, or if present, thefourth gear set; a third gear mechanism between the input shaft and thesecond counter shaft, the second and third gear mechanisms extending inparallel with one another between the input shaft and the second countershaft, the third gear mechanism having a fifth gear set, optionally asixth gear set and a third switching clutch for selectively establishinga power transmission path between the input shaft and the second countershaft via the fifth gear set, or if present, the sixth gear set; and atransmission case 12 supporting and covering most of the input shaft,the first counter shaft, the second counter shaft, the output shaft, thefirst gear mechanism, the second gear mechanism and the third gearmechanism; wherein the first gear mechanism and the second gearmechanism are arranged relatively close to the engine, the third gearmechanism is arranged at a position more remote from the engine than thesecond gear mechanism, and the first counter shaft is arranged above theinput shaft and the second counter shaft, a driving gear of the secondgear set, serves also as the driving gear of the third gear set and isaxially aligned with the ends of the second and third gear sets closerto the engine, and a driving gear of the first gear set is arranged atan axial distance from the engine substantially corresponding to theaxial location of the third switching clutch, and wherein thetransmission case includes a back wall portion formed with a first backwall portion corresponding to the second gear mechanism and the thirdgear mechanism and a second back wall portion corresponding to the firstgear mechanism and located closer to the engine than the first back wallportion, thereby forming a cut-out portion at an upper portion of theback wall portion, and wherein the transmission is connected to theengine and transversely mounted on the vehicle body so that one of thepair of the side frames extending along the both sides of the vehiclebody in the front-rear direction thereof extends through the cut-outportion.
 2. The vehicle according to claim 1, further comprising: areverse movement switching gear mechanism including a reverse shaftarranged in parallel to the input shaft and connected to the outputshaft, a reverse gear set provided between the input shaft and thereverse shaft and a reverse movement switching clutch establishing apower transmission path established by the reverse gear set between theinput shaft and the reverse shaft, wherein the first gear set of thefirst gear mechanism is positioned more remotely from the engine thanthe second gear set and is a gear set for a low speed shift stage, andthe reverse movement gear mechanism includes a driving gear provided atthe input shaft, a driven gear rotatably supported at the reverse shaftand tolerably connectable to the reverse shaft by means of the reversemovement switching clutch and an idler gear rotatably supported at thefirst counter shaft and engaged with the driving gear and the drivengear, wherein the driving gear and the idler gear of the reverse gearset serve also as a driving gear and a driven gear of the first gear setrespectively, of the first gear mechanism.
 3. The vehicle according toclaim 2, wherein the idler gear further includes a first idler gearrotatably supported at the first counter shaft and engaged with thedriving gear, and a second idler gear, whose diameter is smaller thanthat of the first idler gear, integrally formed with the first idlergear but spaced therefrom in the axial direction of the first countershaft and engaged with the driven gear, wherein the driving gear and thefirst idler gear of the reverse gear set serve also as the driving gearand the driven gear, respectively, of the first gear set provided at thefirst gear mechanism.
 4. The vehicle according to claim 1, wherein thefirst gear mechanism includes the first gear set, the second gear setand the first switching clutch arranged therebetween to selectivelyestablish a first or a second speed range power transmission pathbetween the input shaft and the first counter shaft, the second gearmechanism includes the third gear set, the fourth gear set and thesecond switching clutch arranged therebetween to selectively establish athird or a fourth the power transmission path between the input shaftand the second counter shaft, and the third gear mechanism includes thefifth gear set, the sixth forward movement shift stage gear set and thethird switching clutch arranged therebetween to selectively establish afifth or a sixth the power transmission path between the input shaft andthe second counter shaft.
 5. The vehicle according to claim 2, whereinthe first gear mechanism includes the first gear set, the second gearset and the first switching clutch arranged therebetween to selectivelyestablish a first or a second speed range power transmission pathbetween the input shaft and the first counter shaft, the second gearmechanism includes the third gear set, the fourth gear set and thesecond switching clutch arranged therebetween to selectively establish athird or a fourth the power transmission path between the input shaftand the second counter shaft, and the third gear mechanism includes thefifth gear set, the sixth forward movement shift stage gear set and thethird switching clutch arranged therebetween to selectively establish afifth or a sixth the power transmission path between the input shaft andthe second counter shaft.
 6. The vehicle according to claim 3, whereinthe first gear mechanism includes the first gear set, the second gearset and the first switching clutch arranged therebetween to selectivelyestablish a first or a second speed range power transmission pathbetween the input shaft and the first counter shaft, the second gearmechanism includes the third gear set, the fourth gear set and thesecond switching clutch arranged therebetween to selectively establish athird or a fourth the power transmission path between the input shaftand the second counter shaft, and the third gear mechanism includes thefifth gear set, the sixth forward movement shift stage gear set and thethird switching clutch arranged therebetween to selectively establish afifth or a sixth the power transmission path between the input shaft andthe second counter shaft.
 7. A transmission adapted to be axiallyconnected with an engine and adapted to be transversely mounted on avehicle body, comprising: an input shaft adapted to be rotatably drivenby the engine; an output shaft connected to a driving wheel; a firstcounter shaft arranged in parallel to the input shaft and connected tothe output shaft; a second counter shaft arranged in parallel to theinput shaft and connected to the output shaft; a first gear mechanismbetween the input shaft and the first counter shaft, the first gearmechanism having a first gear set, a second gear set and a firstswitching clutch provided between the first and second gear sets toselectively establish a power transmission path between the input shaftand the first counter shaft via either the first gear set or the secondgear set; a second gear mechanism between the input shaft and the secondcounter shaft, the second gear mechanism having a third gear set,optionally a fourth gear set and a second switching clutch toselectively establish a power transmission path between the input shaftand the second counter shaft via the third gear set or, if present, thefourth gear set; a third gear mechanism between the input shaft and thesecond counter shaft, the second and third gear mechanisms extending inparallel with one another between the input shaft and the second countershaft, the third gear mechanism having a fifth gear set, optionally asixth stage gear set and a third switching clutch provided between thefifth and sixth gear sets to selectively establish a power transmissionpath between the input shaft and the second counter shaft via the fifthgear set or, if present, the sixth gear set; and a transmission case 12supporting and covering most of the input shaft, the first countershaft, the second counter shaft, the output shaft, the first gearmechanism, the second gear mechanism and the third gear mechanism;wherein the first gear mechanism and the second gear mechanism arearranged relatively close to the engine, the third gear mechanism isarranged at a position more remote from the engine than the second gearmechanism, and the first counter shaft is arranged above the input shaftand the second counter shaft, a driving gear of the second gear setserves also as the driving gear of the third gear set and is axiallyaligned with the ends of the second and third gear sets closer to theengine, and a driving gear of the first gear set is arranged on theinput shaft at an axial distance from the engine substantiallycorresponding to the axial location of the third switching clutch, andwherein the transmission case includes a back wall portion formed with afirst back wall portion corresponding to the second gear mechanism andthe third gear mechanism and a second back wall portion corresponding tothe first gear mechanism and located closer to the engine than the firstback wall portion, thereby forming a cut-out portion at an upper portionof the back wall portion.
 8. The transmission according to claim 7,further comprising: a reverse movement gear mechanism including areverse shaft arranged in parallel to the input shaft and connected tothe output shaft, a reverse gear set provided between the input shaftand the reverse shaft and a reverse movement switching clutchestablishing a power transmission path established by the reverse gearset between the input shaft and the reverse shaft, wherein the firstgear set of the first gear mechanism is positioned more remotely fromthe engine than the second gear set and is a gear set for a low speedshift stage, and the reverse movement gear mechanism includes a drivinggear provided at the input shaft, a driven gear rotatably supported atthe reverse shaft and rotatably connectable to the reverse shaft bymeans of the reverse movement switching clutch and an idler gearrotatably supported at the first counter shaft and engaged with thedriving gear and the driven gear, wherein the driving gear and the idlergear of the reverse gear set serve also as a driving gear and a drivengear of the first gear set respectively, of the first gear mechanism. 9.The transmission according to claim 8, wherein the idler gear furtherincludes a first idler gear rotatably supported at the first countershaft and engaged with the driving gear and, a second idler gear, whosediameter is smaller than that of the first idler gear, integrally formedwith the first idler gear but spaced therefrom in the axial direction ofthe first counter shaft and engaged with the driven gear, wherein thedriving gear and the first idler gear of the reverse gear set serve alsoas the driving gear and the driven gear, respectively, of the first gearset provided at the first gear mechanism.
 10. The transmission accordingto claim 7, wherein the first gear mechanism includes the first gearset, the second gear set and the first switching clutch arrangedtherebetween to selectively establish a first or a second speed rangepower transmission path between the input shaft and the first countershaft, the second gear mechanism includes the third gear set, the fourthgear set and the second switching clutch arranged therebetween toselectively establish a third or a fourth power transmission pathbetween the input shaft and the second counter shaft, and the third gearmechanism includes the fifth gear set, the sixth gear set and the thirdswitching clutch arranged therebetween to selectively establish a fifthor sixth power transmission path between the input shaft and the secondcounter shaft.
 11. The transmission according to claim 8, wherein thefirst gear mechanism includes the first gear set, the second gear setand the first switching clutch arranged therebetween to selectivelyestablish a first or a second speed range power transmission pathbetween the input shaft and the first counter shaft, the second gearmechanism includes the third gear set, the fourth gear set and thesecond switching clutch arranged therebetween to selectively establish athird or a fourth power transmission path between the input shaft andthe second counter shaft, and the third gear mechanism includes thefifth gear set, the sixth gear set and the third switching clutcharranged therebetween to selectively establish a fifth or sixth powertransmission path between the input shaft and the second counter shaft.12. The transmission according to claim 9, wherein the first gearmechanism includes the first gear set, the second gear set and the firstswitching clutch arranged therebetween to selectively establish a firstor a second speed range power transmission path between the input shaftand the first counter shaft, the second gear mechanism includes thethird gear set, the fourth gear set and the second switching clutcharranged therebetween to selectively establish a third or a fourth powertransmission path between the input shaft and the second counter shaft,and the third gear mechanism includes the fifth gear set, the sixth gearset and the third switching clutch arranged therebetween to selectivelyestablish a fifth or sixth power transmission path between the inputshaft and the second counter shaft.